Electrothermally actuated electrical switch



Aug. 22, 1933.

E. ROZUMEK ELECTROTHERMALLY ACTUATED ELECTRICAL SWITCH Filed Jim 24, 1950 m F/GJ m Unrema'r ttys.

Patented Aug. 22, 1933 PATEN'E OFFICE ELECTROTHERMALLY ACTUATED ELECTRICAL SWITCH Ernst Rozumek, Stockholm, Sweden Application June 24, 1930, Serial No. 463,506, and in Germany July 1, 1929 6 Claims. (Cl. 200113) Electric switch protectors and relays are so far being principally controlled electro-magnetically. However, there are also switches known being actuated by the thermic longitudinal change of metal parts taking place owing to the heat of the current. The former embody the disadvantage, that their switch-spools represent inductive loads, the cutting out of which strongly attacks the contacts provided for that purpose, for which reason it is, e. g. not possible to control such switches in safe working order through the medium of temperature regulators with creeping contact movement or with the aid of contact thermometers. The latter incorporate the disadvantage, that they are extremely inert, acting only after a comparatively long period or else that their control requires comparatively high intensities of current.

In contra-distinction thereto the object of the present invention represents an essential improvement, consisting therein, that the load of the controlling contacts is non-inductive, the period of acting very short and finally, that the intensity of the controlling current and controlling power is very low.

In accordance with the invention a very fine wire, possessing as high a thermic coefficient of expansion as possible, is so wound up in several long stretched windings, that the separate windings uniformly expand under the influence of the heat of the current and that each winding is made to act upon the contacts to be actuated with the same tensile force. The total resistance of these windings electrically connected in series may, at the same time, easily be so adjusted, that the winding, if necessary using a series resistance for that purpose, allows of being immediately connected with the existing voltage of the system.

With the aid of the accompanying drawing, which represents a few examples of performance, the essential features of the present invention will be described in detail.

Fig. 1 represents a thermically controlled switch in accordance with the invention in front view.

Fig. 2 is a lateral view of the inner parts of same.

Fig. 3 shows a switch of a somewhat modified form of construction, partly in section.

Fig. 4 is a top view of the inner parts shown in Fig. 3, and

Fig. 5 is a longitudinal sectional view of a switch in accordance with another form of construction, whilst Fig. 6 is a fragmentary section of a switch in accordance with a further form of construction.

In conjunction with the form of construction according to Figs. 1 and 2 a bus-bar 1 is made to support the fixed contact 2. At the upper end of the bus-bar 3 a spring 4 has been attached, the elasticity of which is pressing the movable contact 5, fastened thereto, in an upward direction. The expansion-wire 6 is wound over 2 rolls 7 and 8 consisting of an insulating material. The roll 7 is attached to the bus-bar l by means of the stirrup 11. The roll 8 has been suspended to the contact-spring 4 by means of the stirrup '12. The expansion winding 6 has been so connected, that, when being in a cold state, it closes the contacts 2 and 5. If it is subjected to heat, however, the separate windings will be made to expand almost instantaneously owing to their small cross sectional area, the contact-spring 4 will be relieved, causing the contacts 2 and 5 to open, After interruptng the control-current, the windings will cool down just as quickly, subsequently contracting again and thereby close the contacts. The tensile force exercised by the spring 4, is the sum of the separate tensile forces of the separate Wires of the winding. Although utilizing very fine wires, the tensile force exercised is strong enough to guarantee a reliable and safe working. The resistance of the total winding is so high in conjunction therewith, that the winding, if necessary using a small series resistance for that purpose, allows of being immediately connected with the existing voltage of the system. The parts of the switch are suitably enclosed in a vessel, e. g. of glass, as indicated at A, which has been evacuated or charged with an indifferent gas.

1a and 3a indicate lead-in wires for the bars 1 and 3 and 9 and 10 indicate lead-in wires for the expansion wire 6, the several wires 1a. and 3a, 9 and 10 being sealed in the wall of the vessel A.

Figs. 3 and 4 represent another form of construction, in which the winding 13 has been placed round the contacts 16 and 17 concentrically in long zigzag windings or turns by means of the two winding-supports 14 and 15.

One contact 16 is provided with a screw whereby the winding wires 13 are so tensioned that the contacts 16, 1'7 touch eachother in the unheated state of their windings.

A guiding member 31a is inserted in a tube 31 for the movable contact 16. A spring 18 is inserted between the said guiding member and the nut 15a.

If current passes through the windings 13 and thereby heats them so that they expand, the contact 16 will be lifted from the contact 17 by the spring 18 thereby interrupting the current. The whole system is enclosed in a vacuum-tight vessel A as according to the subject matter of Figure 1.

Conducting members 16a, 17a, 13a, 13b are 1 provided, which penetrate the vacuum-tight tatable small rolls.

closed vessel and lead the electric current to the resistance wires 13 and the contacts 16, 1'7.

This arrangement embodies the advantage, particularly in conjunction with the employment of vacuum-switches, that it adapts itself very well to the form of the glass-tube, in which these switches are usually enclosed.

A further form of construction has been shown in Fig. 5. In this instance the expansion-winding 19 is wound over a strip 22 in its longitudinal direction by means of two insulating rolls 20 and 21. The separate windings or turns are held under tension through the medium of the contact-springs 25 and 26, simultane ously interpolating two insulating pieces 23 and 24. A vacuum-tight closed vessel A encloses all parts. Conducting members 25a, 26a, and 19a, 19b are passed through the vessel A.and lead the current to the contacts 2'7 and 28 and to the winding 19 of the resistance wire, respectively. If there is no current in the winding, the contacts 2'7 and 28 will be closed. If the winding is subjected to heat, the separate wires will be made to expand, thereby causing the contacts to open. This arrangement possesses the advantage, that the expansion through heat of the separate wires may be transferred to the contacts in any desired multiplication.

In view of the fact, that the separate windings or turns are mutually heating each other, the inner windings or turns will expand more than those situated externally. For this reason the latter may be stressed mechanically to a higher degree. It is, therefore, advisable, to wind the external windings correspondingly closer, in order to thus attain a uniform heating and expansion of the separate windings or turns.

The same purpose, i. e. the uniform mechanical strain of the separate windings or turns, will also be thereby attained, that the separate windings or turns are capable of equalizing themselves whilst working. This -may be rendered possible, e. g. by causing the insulating rolls carrying the winding, to consist of separate, ro-

It will likewise be suflicient to glaze the insulating rolls, thus rendering it possible for the wire to glide upon them.

For the purpose of avoiding an uneven load of the separate windings or turns, it will be advisable to suspend at least one of the insulating rolls in points only, as it may be gathered from Fig. 1. The pin-screw 29 is made to serve in this case as a point-like support and simultaneously renders it possible to adjust the winding.

In case, that the present invention is to be incorporated in vacuum switches, it is suggested to produce the expansion wire from the vacuum molten material.

In order to protect the fine expansion wire from the effects of the discharge phenomena when opening the contacts, particularly with vacuum switches, it is advisable to screen the winding from neighbouring parts under tension. The numeral 30 in Fig. 1 shows an example of arrangement of such a screen, which may be made to consist of. an insulating material or of a conducting material, if desired. In the arrangement according to Fig. 3, the distance tube 31 used in, the construction simultaneously assumes the functions of a screen.

It may occasionally be necessary to transmit to the contacts the values yielded by the dimensioning of thewinding in regard to expansion and tensile force. In such cases a lever transmission will have to be provided between the loose roll and the movable contact. This has been shown in Fig. 6 by way of example. The movable contact 32 has in this instance been attached to the bus-bar 34 by means of the spring 33. At the bent-over end of the contact-spring 33 the lever 35 is made to engage,

its centre of motion being the end of the. busbar 34. The movable insulating roll carries one of the ends of the expansion winding 3'7. In the arrangement according to Fig. 6 the heating of the winding corresponds to a closing of the contacts.

For the purpose of protecting the winding from mechanical overload, the arrangement should be suitably such, that between the point of suspension of the winding and the'movable contact an elastic member is interpolated, capable of still yielding a little, when the contacts have already been closed.

For the construction of the switch, in particular for the bus-bar, a material is suitably taken which possesses a low thermic coefiicient of expansion.

The object of the present invention is not confined to the examples of performance referred to; they represent, as a matter of fact, only a few suggested constructions.

I claim:

1. An electro-thermally actuated electric switch comprising in combination, mechanically parallel and electrically series connected resistance wires, supports maintaining said wires under tension, contacts secured to the supports, a vacuum-tight closed vessel enclosing the wires,

' supports and contacts and constituting a bearer -for the latter, and conducting members passing through the vacuum-tight closed vessel and leading the electric current to the resistance wires and the contacts.

2. An electro-thermally actuated electric switch comprising in combination, mechanically parallel and electrically series connected resistance wires, supports maintaining said wires under tension, contacts secured to the supports, a vacuum-tight closed vessel enclosing the wires, supports and contacts and constituting a bearer for the latter, an insulating screen arranged between the wires and the contacts, and conducting members passing through the vacuum-tight closed vessel and leading the electric current to the resistance wires and the contacts.

3. An electro-thermally actuated electric switch comprising in combination, mechanically parallel and electrically series connected resistance wires, supports maintaining said wires under tension, contacts secured to the supports,

the supports of the wires and regulating the tension of the latter and the switch path of the contacts, and conducting members passing through the vacuum-tight closed vessel and leading the electric currentto the resistance wires and the contacts.

4. An electro-thermally actuated electric switch comprising'in combination, mechanically parallel and electrically series connected resistance wires, supports maintaining said wires under tension, contacts secured to the supports, a vacuum-tight closed vessel enclosing the wires, supports and contacts and constituting a bearer for the latter, a set screw acting on one of the supports of the wires and regulating the tension of the latter and the switch pathof the contacts, an insulating screen arranged between the wires and the contacts, and conducting'members passing through the vacuum-tight closed vessel and leading the electric current to the resistance wires and the contacts.

5. An electro-thermally 4 actuated electric switchcomprising in combination, mechanically parallel and electrically series connected resistance wires, disc-shaped supports maintaining said wires under tension,.contacts secured to the wire supports, a cylindrical insulating screen arranged between the wires and the contacts, and conducting members passing through the vacuum-tight closed vessel and leading the electric current to the resistance wires and the contacts.

6. An electro-ther'mally actuated electric switch comprising in combination, mechanically parallel and electrically series connected resistance wires, disc-shaped supports maintaining said wires under tension, contacts secured to the wire supports, a cylindrical insulating screen arranged between the wires and the contacts, a vacuum-tight vessel enclosing the screen, supports, wires and contacts, and conducting members passing through the vacuum-tight closed vessel and leading the electric current to the resistance wires and the contacts.

ERNST ROZUMEK. 

